In recent years, with the spread of computers, ink jet printers have been widely used to print on paper, film, cloth, etc. at offices as well as at home.
Examples of ink jet recording method include a method which allows a piezoelectric element to give pressure that causes a droplet to be ejected, a method which comprises heating the ink to generate bubbles, causing a droplet to be ejected, a method involving the use of ultrasonic wave, and a method which uses electrostatic force to suck and discharge a droplet. As inks for these ink jet recording methods there are used aqueous inks, oil-based inks and solid (melt type) inks. Among these inks, aqueous inks are mainly used currently because they are relatively better than oil-based inks and solid (melt type) inks from the standpoint of possibility of attaining producibility, handleability, odor, safety, etc.
The dyes to be incorporated in these inks for ink jet recording are required to exhibit a high solubility in solvents (ink medium), allow a high density recording and have a good hue and an excellent fastness to light, heat, air, water and chemical, a good fixability to image-receiving materials, difficulty in running, an excellent preservability as an ink, no toxicity and a high purity and be available at a low cost. However, it is extremely difficult to seek coloring agents meeting these requirements to a high extent. In particular, excellent hue and fastness are contrary to each other in most cases, making it difficult to obtain coloring materials for magenta ink that can satisfy the aforesaid requirements and particularly difficult to find out dyestuffs which exhibit a good magenta hue and a light fastness high enough to withstand an oxidizing atmosphere at the same time.
Accordingly, although various dyes or dyestuffs for ink jet have been already proposed and practically used, it is the present situation that no dyestuffs that satisfying all the aforesaid requirements have been found yet.
Known dyes and pigments provided with color index (C.I.) number can difficultly satisfy both the hue and fastness requirements for inks for ink jet recording.
As a dye which can enhance fastness there has been proposed an azo dye derived from an aromatic amine and a 5-membered heterocyclic amine described in Patent Reference 1 cited below. However, these dyes have an undesirable hue in the yellow and cyan ranges and thus are disadvantageous in that they deteriorate color reproducibility.
Patent References 2 and 3 cited below disclose inks for ink jet recording for the purpose of accomplishing both hue and light fastness. However, the dyestuffs used in these publications have an insufficient water solubility when used as water-soluble ink. Further, the dyestuffs described in these publications are disadvantageous also in wet heat fastness when used as water-soluble ink for ink jet.
As means for solving these problems there have been proposed an improved magenta dyestuff and an ink composition using the same described in Patent Reference 4 cited below. Further, an ink for ink jet recording which comprises a pyrazolylaniline azo dyestuff to improve hue and light fastness is also described (Patent Reference 5 cited below). However, these inks for ink jet recording leave something to be desired both in color reproducibility and fastness of output image.
Further, it was made obvious that there are some cases where an image recorded on a gloss paper of photographic image quality dedicated to ink jet exhibits a remarkably poor image preservability when put on the wall of a indoor room. The present inventors presume that this phenomenon is attributed to some oxidizing gases such as ozone in the air. Further, the blockade of air flow such as by enclosure in a glass frame makes it difficult for this phenomenon to occur, but this limits the working conditions.
This phenomenon is remarkable particularly with gloss paper of photographic image quality dedicated to ink jet and thus raises a great problem with the current ink jet recording process, which is required to provide a desired photographic quality image as one of important features.
[List of Patent References of Related art]
    [Patent Reference 1]    JP-A-55-161856    [Patent Reference 2]    JP-A-61-36362    [Patent Reference 3]    JP-A-2-212566    [Patent Reference 4]    JP-T-11-504958    [Patent Reference 5]    JP-A-2000-80733
An aim of the present invention is to solve the problems with ink for ink jet recording described above with reference to the related art technique and more specifically is to provide a magenta ink for ink jet recording excellent in weathering resistance. An additional object of the present invention is to provide a magenta ink for ink jet recording which is preferably provided with a hue as magenta ink, exhibits a high stability in ejection and causes no defects in water resistance and image quality in addition to the aforesaid requirement.